Electrophysiological heterogeneity and stability of reentry in simulated cardiac tissue

Generation of wave break is a characteristic feature of cardiac fibrillatio n. In this study, we investigated how dynamic factors and fixed electrophys iological heterogeneity interact to promote wave break in simulated two-dim ensional cardiac tissue, by using the Luo-Rudy (LR1) ventricular action pot ential model. The degree of dynamic instability of the action potential mod el was controlled by varying the maximal amplitude of the slow inward Ca2current to produce spiral waves in homogeneous tissue that were either near ly stable, meandering, hypermeandering, or in breakup regimes. Fixed electr ophysiological heterogeneity was modeled by randomly varying action potenti al duration over different spatial scales to create dispersion of refractor iness. We found that the degree of dispersion of refractoriness required to induce wave break decreased markedly as dynamic instability of the cardiac model increased. These findings suggest that reducing the dynamic instabil ity of cardiac cells by interventions, such as decreasing the steepness of action potential duration restitution, may still have merit as an antifibri llatory strategy.